Various portable power grinding machines have been disclosed, and have appeared on the market. These portable power grinding machines are widely invited for the advantage of mobility. In recent years, DIY (do-it-yourself) furnitures and apparatus have become more and more popular. Therefore, the demand for portable power grinding machines is more and more stronger. However, the grinding heads of regular portable power grinding machines are commonly not replaceable and designed for a specific use only. Therefore, for different grinding purposes, different grinding machines shall be prepared.